The present invention relates to a telescopic remote manipulator of the master-slave type and more specifically relates to the systems by cables, bands or any similar means within such a manipulator, which make it possible to transmit from the slave side the movements performed on the master side of the manipulator. Throughout the text, the term cables or bands will be used to designate all similar means making it possible to fulfil such a function.
It is known that manipulators of the master-slave type comprise a master arm equipped with a control handle accessible to an operator and a slave arm, which is generally identical to the master arm and which is equipped with a tool, such as a gripping claw or the like. The slave arm is disposed within a cell which is not accessible to the operator, due to the presence of an atmosphere or dangerous products, such as radioactive products within the said cell. The master arm and the slave arm are provided with the same number of degrees of freedom and are mechanically connected through the cell wall in such a way that any movement of the master arm and/or its control handle controlled by the operator leads to identical movement of the slave arm and/or the gripping claw. A window made in the partition or bulkhead of the cell thus makes it possible for the operator to remotely carry out the desired manipulations within the cell.
Furthermore, master-slave remote manipulators are subdivided into two basic groups. The first of these groups involves articulated manipulators in which the master and slave arms in each case comprise several articulated segments, which reproduce movements comparable to those of the human arm, in the most frequent arm when there are two such segments. The second group is that to which the present invention refers and involves telescopic manipulators in which each arm comprises several segments mounted in telescopic manner, in order to permit a modification to the length of these arms.
More specifically, the master-slave telescopic manipulator according to the invention comprises a telescopic master and slave arm, said arms being articulated to a passage or traverse block about two shoulder pins, which are normally parallel to one another and orthogonal to the axis of the block, which passes through the cell partition and is mounted so as to rotate about its own axis. The end of each of these arms consequently has three degrees of positioning freedom.
Moreover, at each of the ends of these arms there is a toggle joint on which is mounted the control handle for the master arm and the gripping claw for the slave arm. Each toggle joint rotates relative to the arm axis corresponding thereto and also permits the rotation of the handle and claw on the one hand about an axis orthogonal to the axis of the arm, and on the other hand about its own axis. Finally, the opening and closing of the claw can be controlled by manipulating a trigger or catch on the control handle. These degrees of freedom linked with the handle and claw are generally called degrees of orientation freedom.
By convention, hereinafter the degrees of positioning and orientation freedom will be designated as follows:
X: rotation of the arms about the axis of the passage block; PA1 Y: rotation of the arms about their shoulder pin; PA1 Z: variation of the length of the arm; PA1 A: pivoting of the toggle joint about the axis of the arm; PA1 B: pivoting of the handle and claw about an axis orthogonal to the axis of the arm; PA1 C: pivoting of the handle and claw about its own axis.
The claw opening and closing movements are added to these degrees of freedom.
In order to increase the scope of remote manipulators and facilitate accessibility to certain areas of the cell, they are generally equipped with means making it possible to bring about a displacement of the slave arm relative to the master arm, in accordance with one or more degrees of freedom X, Y and Z and independently of any movement of the master arm. In view of the possibility of displacing the length of the slave arm relative to that of the master arm, the slave arm is generally constituted by three segments, which are respectively called the upper segment, the intermediate segment and the lower segment, whilst the slave arm only comprises two segments, which are called the upper segment and the lower segment.
As is known, the transmission to the slave arm of the movements in Z of the master arm, as well as the transmission to the gripping claw of all the movements A, B and C of the control handle, including movement D corresponding to the closing of the claw, are realised along each of the said arms by means of cables, bands or any similar system, whereby at least one cable or band is provided for each of these movements. In order to preserve the sealing of the passage through the cell partition, the transmission of the movements Y, Z, A, B, C and D through said partition takes place by rotary shafts which are parallel to the axis of the passage block and extend within the latter over at least the width of the partition. Transmission of movements between these rotary shafts and the corresponding cables or bands takes place, both on the master and slave side, e.g. by means of angle return pinions, whereof one is carried by the shaft and the other is integral with a capstan on which is wound the cable or band.
It is necessary to provide means on both the master and slave arm sides, as well as for each of the cables ensuring transmission to the gripping claw movements A, B, C, and D imparted to the control handle, for compensating any length variation of the respective arm, so that the length variation has no effect on the transmission of the A, B, C, and D movements. This variation may only be manual for the master arm or either manual or electric for the slave arm. This also applies to the cable of the slave arm ensuring the transmission to the latter of variations in the elongation Z of the master arm, because it is necessary to ensure that an elongation of the electrically controlled slave arm has no effect on the said movement.
In order to solve these compensation problems, in a first type of telescopic manipulator it is proposed to carry out this compensation on the slave arm by providing on each of the cables controlling movements, A, B, C and D of the gripping claw a pulley block system within the arm and which is used for compensating manual variations of the elongation Z and a mobile carriage or slide outside the slave arm and used for compensating electrical variations of the elongation of this arm. It is obvious that only on the side of the master arm is the pulley block system located within the same in order to compensate length variations thereof. This arrangement makes it possible to use the same carriage for compensating on the cable controlling the manual elongation of the slave arm, the variations in the length of said arm resulting from the control of an electrical displacement. However, it has the disadvantage of causing a serious problem of overall dimensions, particularly with respect to the slave arm, as a result of the presence of pulley blocks within said arm, together with a cabling problem due to the complexity of the system leading to a large amount of friction. This disadvantage is made all the more serious in that it tends to reduce the service life of the cables or bands, which leads to serious effects on the efficiency of such a manipulator, due to the complexity of the interventions required on the slave arm.
Telescopic manipulators are also known in which these problems are solved in a rather different way. These manipulators are characterized by the fact that the elongation controls of the slave arm are carried out by means of a single cabling system for the manual control and for the electrical displacement control. It is therefore no longer necessary to provide for compensation on the cables ensuring the control of the different movements of the gripping claw. Thus, the intermediate segment of the slave arm then moves over a distance equal to half that by which the lower segment moves, so that the said compensation is automatically ensured by the advance of the cables between the intermediate segment and the upper segment. However, this system has the disadvantage that any slave arm extension movement of either a manual or electrical nature, leads to double friction between the different segments of the slave arm, which is not desirable for obvious mechanical reasons.